1. Field of the Invention
The present invention relates to an organic electroluminescence device (hereinafter, simply abbreviated as “organic EL device”) used for a flat device display or the like.
2. Description of the Related Art
In recent years, an organic EL device as a self-luminous device for a flat device display has received attention. Organic EL devices are classified into a top emission type and a bottom emission type depending on device structure.
An organic EL device easily causes characteristic degradation due to water or oxygen. It is known that even a small amount of water may cause peeling of an organic compound layer and an electrode layer, and produce dark spots. Therefore, an organic EL device is sealed with a sealing member (for example, etching glass cover) having a moisture absorbent placed inside, and the moisture absorbent removes water and oxygen infiltrating into the organic EL device, thereby ensuring a lifetime of the organic EL device.
As one example, Japanese Patent Application Laid-Open No. 2002-008852 discloses a technique in which a deoxidized and dehydrated portion having an alkali metal or an alkali earth metal is formed at any position inside a sealed space.
Further, Japanese Patent Application Laid-Open No. 2005-079056 discloses a technique in which ceramics such as zeolite or a metal oxide such as calcium oxide is placed inside a sealed space.
The above technique of Japanese Patent Application Laid-Open No. 2002-008852 is effective in a bottom emission type organic EL device since an alkali metal or an alkali earth metal has a metallic luster. However, it is difficult to employ the technique in a top emission type organic EL device since light extraction efficiency and the efficiency of deoxidization or dehydration are mutually contradictory. Further, since film formation of these materials is performed by a sputtering method or the like, these materials have a problem in costs.
The above technique of Japanese Patent Application Laid-Open No. 2005-079056 has a problem of having difficulty in optical adjustment when the technique is adopted for a top emission type organic EL device, because the metal oxide is a solid particle and has a large size in shape.